Investigation into the structure and function of the nuclear lamina is proposed. Primary organisms of study will be Drosophila melanogaster and Saccharomyces cerevisiae. Sites of posttranslational modification of the Drosophila lamin will be mapped and the role of posttranslational modifications in regulating nuclear lamina form and function will be explored. In vitro mutagenesis of the cloned Drosophila lamin gene and in vivo genetic analyses will be employed in this effort. The biochemistry of nuclear lamina assembly and disassembly will be investigated using cell- free systems. The cloned Drosophila lamin gene will be expressed in the yeast, Saccharomyces cerevisiae. Posttranslational processing, subcellular localization and behavior during the cell cycle will be determined. The results of these investigations will add to our understanding of the maintenance of nuclear form and function during normal growth and in times of cellular stress (e.g. heat shock/hyperthermia), as well as during differentiation and development. Insights into the regulation of nuclear disassembly and reassembly in mitosis and meiosis are also anticipated.